THE GLACIAL PERIOD. 



193 



rocks, which were recognised by Mr. Around Helland. 1 And 

 Mr. Plant mentions the occurrence in boulder-clay farther 

 inland, at Leicester, of certain " hornblendic-looking masses, 

 neither dolerite nor diorite, but fibrous or slaty rather than 

 granular," 2 which are possibly also of Norwegian origin. 

 Doubtless, when the geologists of the Midland Counties have 

 exhausted the investigation of the older glacial deposits of these 

 districts, we may expect to hear of many similar " finds." 



The ice which would thus appear to have streamed trans- 

 versely across England eventually coalesced with that which 

 overflowed from the basin of the Irish Sea south-east through 

 Cheshire, together with that which streamed east from the 

 Welsh Uplands, and the united mer de glace thereafter made its 

 way into the Bristol Channel. Here it joined the thick ice 

 that flowed out to sea from the high grounds of South Wales — 

 the bottom -moraine of which is conspicuous not only in the 

 mountain-valleys of that region, but also upon the low-lying 

 tracts that extend from the hills to the sea. In the south- 

 eastern counties, so far as we know at present, the ice-sheet at 

 the climax of the Glacial Period did not extend farther than 

 the valley of the Thames, beyond which no trace of its bottom- 

 moraine has been met with. 3 



The pressure exerted by the ice -sheet as it crept over 

 England is well shown by the size of the great erratics of chalk, 

 which are here and there enclosed in the boulder-clay of East 

 Anglia. These have evidently been displaced and carried for- 

 ward along with the sub-glacial debris with which they are 

 associated. Some of the blocks referred to are so large that 

 they have been quarried. Many occur in Norfolk, where they 



1 Zeitschr. deutsch. geol. Ges., 1879, p. 67 ; Archiv for Mathematik og Natur- 

 vidensTcab. , 1879, p. 287. See further on this subject Appendix B. 



2 Brit. Assoc. Rep., 1874, p. 197. 



3 For fuller details I may be allowed to refer to Great Ice Age, chaps, xxviii.-xxx. 

 where references will be found to various authorities for the facts upon which the 

 above conclusions are based. Mr. S. V. Wood's papers on the glacial geology of 

 East Anglia will be found particularly instructive, and I say this not the less 

 readily, because I find myself compelled to dissent from some of his theoretical 

 views. 







